Discriminating ability of the Infant Neurological International Battery

Transcription

1 Discriminating ability of the Infant Neurological International Battery (Infanib) for the neurological outcome of high-risk infants in a cohort of 5857 low birth weight infants followed during their irst year of corrected age in a Kangaroo Mother Care Program in Bogota, Colombia. Ana María De la Hoz, Research asistant, Kangaroo Foundation Nathalie Charpak, Pediatrician, Kangaroo Foundation Fabián Gil, Biostatistician, Department of Epidemiology, Javeriana University Juan Gabriel Ruiz, Pediatrician, Epidemiologist, Deparment of Epidemiology, Javeriana University

2 Introduction At the Kangaroo Mother Care Program in Bogota, the Neurological International Battery (Infanib) has been used as a neuromotor integrity screening tool for nearly 20 years in order to make a timely intervention of possible neuromotor chronic disorders in premature/lbw infants. Screening is performed at 3, 6, 9 and 12 moths of corrected age and, according to results, interventions including physical therapy, further testing and reference to pediatric neurology are performed. Infanib is a practical and short time performing test that can be easily integrated into the periodic follow up evaluations of high risk infants by pediatricians and other health care professionals.

3 Infanib Designed to provide information on age specific motor development impairment, and to identify patients and motor areas that could benefit from early intervention. INFANIB Factor Spasticity Head and trunk Vestibular function Legs French angles Items Asymmetric tonic neck reflex Tonic labyrinthine in prone Tonic labyrinthine in supine Hands held open or closed Sitting Pulled to sitting All fours Body derotative Backward parachute Forward parachute Sideway parachute Body rotative Standing Foot grasp Dorsiflexion of foot Positive support reflex scarf sign heel to ear popliteal angle abductor's angle Classifies motor development as: Normal Transient Abnormal And also has the potential to identify some types of neurological abnormalities: Spastic tetraparesis Spastic hemiparesis Spastic diplegia Hypotonia

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5 Objective To date, no comprehensive assessment of the test applied to preterm/lbw infants follow up program has been conducted The objective of the study was to assess the discriminating ability of the INFANIB performed at 3, 6 and 9 months of CA for detecting neurological abnormal findings at one year CA in preterm and/or low birth weight infants.

6 Method Observational analytic study in a non biased sample of infants from an historical cohort of 6481 infants with a complete follow up during their first year of life in a KMCP in Bogota between 1993 and Inclusion criteria: complete information on neurological outcome at 1 year of corrected age (Griffiths Mental Development Scale and Infanib evaluation) and information regarding at least 1 neuro developmental evaluation at 3, 6 or 9 months of corrected age with Infanib. Neurological outcome at 1 year CA was the reference standard defined as the presence of neurological abnormality given by the results of Griffiths and Infanib (abnormality in any of the two tests, or transient result in both of them).

7 Method The INFANIB test classifies any infant as abnormal, transient and normal. INFANIB result at 3,6 and 9 months was dichotomized as: Abnormal: any abnormal or transient result Normal. Sensitivity, specificity, area under the ROC curve, PPV and NPP were calculated for Infanib evaluations at 3, 6 and 9 months of CA to determine the discriminating ability of Infanib on motor disorders or function at one year CA

8 Results 624 infants excluded due to incomplete or invalid information on neurological evaluation at 1 year of CA: Final sample of 5857 infants included in the analysis. Information of Infanib evaluation at : 3 months: 5812 (99.2%) 6 months: 5801 (99%) 9 months: 5833 (99.5%)

9 General characteristics of the population Characteristic No. % Mean Min-max Birth weight (g) Categorical birth weight (g) Less than1000 g to 1500 g to 2000 gr More than 2000 gr Gestational age at birth (weeks) Categorical gestational age at birth (weeks) 30 or less to to to and more C section Male Acute fetal distress Oxygen dependency NICU IUGR Anoxia IVH

10 Results Neurodevelopmental Outcome at 1 year of corrected age 256/5857 (4.4%) infants with abnormal result in the neurological evaluation Characterisation of adverse outcome at 1 year CA No/total (%) Abnormal result in both tests 45/256 (17.6) Abnormal and a transient result 56/256 (21.9) Abnormal and normal result 59/256 (23.0) Griffiths abnormal - INFANIB normal Griffiths normal - INFANIB abnormal 50/256 (19.5) 9/256 (3.5) Transient result in both tests 96/256 (37.5)

11 Results INFANIB assessments Age of assessment Result No./total (%) 3 months CA N= months CA N= months CA N=5833 Normal 4326/5812 (73.9) Transient 1438/5812 (24.6) Abnormal 48/5812 (0.8) Normal 4185/5801 (71.5) Transient 1532/5801 (26.2) Abnormal 84/5801 (1.4) Normal 5142/5833 (87.8) Transient 609/5833 (10.4) Abnormal 82/5833 (1.4)

12 Neurological impairment at 1 year CA Characteristic Present Absent GA at birth (weeks) N/total (%) 30 or less 87 (34.5) 651 (11.7) (15.5) 821 (14.8) (19) 1700 (30.6) (22.2) 56 (33.6) More than (8.7) 22 (9.2) Birth weight (grams) N/total (%) Less than (16.4) 227 (4.1) (9.8) 288 (5.1) (19.5) 722 (12.9) (24.2) 1336 (23.9) (10.2) 1410 (25.2) More than (19.9) 1617 (28.9) NICU admission N/total (%) 116 (45.3) 1379 (24.6) IVH N/total (%) 49 (19.8) 251 (4.7) Oxygen dependency N/total (%) 131 (51.2) 1162 (20.7) Neonatal anoxia N/total (%) 24 (54.4) 1635 (32) Fetal distress N/total (%) 94 (36.7) 1950 (34.8)

13 Discriminative ability of Infanib Neurological outcome 1 year CA Sensitivity Specificity ROC area PPV NPV Infanib 3 months N= 5812 Abnormal Normal Abnormal n=1486 (%) % (56-68%) Normal n=4326 (%) % (75-77) 0.69 (0.66;0.72) 10% 98% Infanib 6 months N= 5801 Abnormal (n=1616) % (71.8;82.5) Normal (n=4185) % (73.2;75.5) 0.76 (0.73;0.78) 12% 98% Infanib 9 months N=5833 Anormal (n=691) % (71.5;82.2) Normal (n=5142) % (90.4;91.9) 0.84 (0.81;0.87) 28% 99%

14 Discussion Results of the present study seem to confirm that early evaluation with Infanib may have an acceptable predictive validity to neurological outcome at one year of age. Soleimani et al (2006): Evaluation of validity of Infanib in primary care. Infants 4 to 18 months. Sensitivity 90% Specificity 83% (General population) Liao et al (2012): Predictive validity of a Chinese version of Infanib at 3, 7 and 10 months CA on neurological outcomes at 1 year CA. High risk premature and full-term infants Liao et al (2012) (high risk) Our study (high risk) Preterm (n=55) Full-term (n=49) Preterm and/or LBW 3 months 3 months (n=5812) Sensitivity(95%CI) 76.9 (46.2;95) 76.9 (46.2;95) Sensitivity (95%CI) 62.1 (56;68) Specificity 57.1 (41;72.3) 41.7 (25.5;59.2) Specificity 76.1 (75;77) 7 months 6 months (n=5801) Sensitivity 84.6 (54.6;98.1) 84.6 (54.6;98.1) Sensitivity 77.5 (71.8; 82.5) Specificity 57.1 (41;72.3) 72.2 (54.8;85.8) Specificity 74.4 (73.2;75.5) 10 months 9 months (n=5833) Sensitivity 84.6 (54.6;98.1) 92.3 (64;99.8) Sensitivity 77.2 (71.5; 82.2) Specificity 81.0 (65.9; 91.4) 77.8 (60.8;89.9) Specificity 91.1 (90.4;91.9)

15 Discussion Sensitivity of INFANIB is low at 3 months (62%), and statistically significantly different from sensitivities at 6 and 9 months. Sensitivities at 6 and 9 months are almost identical and non statistically different. The value is modest (77%) and not high enough for use as a screening test. Specificity increases steadily with age, the trend is clearly significant.

16 Discussion Overall discriminating ability (area under the ROC curve) also increases steadily with corrected age. These observations are consistent with the fact that abnormalities in neurodevelopment might be originated early (for instance at birth due to asphyxia) but manifestations become evident when the affected structures or functions should develop (maturation). In consequence, the more mature the infant when the evaluation is performed, the better the discriminant ability of the INFANIB test.

17 Discussion Ideal sensitivity of a screening test should be as close as possible to 100% According to this, INFANIB could be judged as insufficient. The issue is that one can not diagnose a problem that has not appeared yet. Neurodevelopment evolves in time, therefore there are abnormalities not present and impossible to detect at certain times, and a screening test or a confirmatory test will not detect them. (One cannot evaluate vocabulary and numerical reasoning or walking ability at 3 months of age). One should not confound diagnosis and prediction. Screening test do not predict but establish a preliminary diagnosis.

18 Discussion In summary although INFANIB at 9 month is not sensitive enough for diagnosis motor outcomes at one year, it detects those infants who do have a problem at 9 months. (Discriminate but do not necessarily predict). A normal Infanib means that the infant should continue under close clinical monitoring. Specificity at 9 months is very high (>90%). Meaning that an abnormal result is very likely to be a true positive finding. The other use of INFANIB is not to diagnose but to timely identify infants likely to benefit from early intervention. INFANIB at 3 and 6 months can help identifying infants in need for early intervention (physical therapy): reflected in a sharp decrease in number of abnormal Infanib results between 6 (1616 ) and 9 months (691)

19 Conclusion Periodic INFANIB testing can be informative and easily included in the routine physical exam made by the paediatrician in kangaroo follow-up programs. Should not be regarded as a screening test for future neuromotor impairment, given that sensitivity is not high enough. I.E. A negative result does not rule out future neuromotor impairment, and normal subjects should continue under close clinical surveillance, including periodic INFANIB testing.

20 Conclusion An abnormal INFANIB test particularly at 9 months should rise concern given the high specificity and prompt for aggressive and timely intervention. The quest for developing or identifying a better screening tool should continue. Thank you